The objective of this study is to use temperature-sensitive mutants of Drosophila melanogaster to study the functions and structure of the nervous system as well as to determine the role of neural tissue in development. A genetic screen using mass-mating techniques will be used to isolate new putative neurological mutants on the X chromosome and autosomes by selecting for mutants with temperature-induced locomotor defects. New mutants will be characterized with respect to their genetic, electrophysiological, and behavioral characteristics and temperature-shift studies will be used to pinpoint periods in development when mutant loci exert their effects. Characterization of the neurological mutant shibire ts will be continued to determine the range of tissue affected by this mutant and to elucidate the mechanisms causing the observed developmental anomalies. These studies will involve intracellular recordings from the retinula and laminar cells of the eye as well as from the indirect flight muscles. We will study development of this mutant in primary tissue culture under conditions in which functional neurons and myocytes should differentiate. Structural changes induced by this mutation during development of sensory receptors will be examined at both the light and electron microscopic level. Fate mapping using genetic mosaics will be used to localize foci responsible for various developmental anomalies.